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Letters from Pinto

18 August 2004

Dear All,
probably I didn't make myself clear.
The grades are on the EE40 class website, don't look for them on

Here is the link:

Again, be honest we yourself first of all, with other students secondly
and we me thirdly.


17 August 2004

Dear All,
the grades have been posted on line. You'll find a link on the webpage.
It is mandatory for me to enter the final grades tomorrow before 4 PM.


17 August 2004

there are errors on the final grades

17 August 2004
It is so late that I might have done some errors in assigning grades.
If you have concerns of this kind please let me know (but be
don't try to ask for a better grades just to give it a try).

Few words before saying good night:
For some of you I was really sorry because I think you could have
gotten a
better grade. For some of you, instead, I know that you probably don't
really deserve what you got.
But again, I do not understand why those numbers have to be given and
is the root of the problem.

Good night


16 August 2004

A lot of students cannot make it tomorrow, so let's reschedule it for
Wednesday August 18th form 12PM to 1PM in 277 Cory Hall.

I know that some of you still cannot make it and I'll let them know the
grade by e-mail.

See you then


16 August 2004
Sorry I forgot time and place

WHEN: Tomorrow, 08/17/2004 5PM
WHERE: 277 Cory Hall, the usual place
WHY: Discussion of final exam.


16 August 2004

Dear All,
Let's meet tomorrow, Tuesday August 17th to discuss the final together.


12 August 2004

My Dear Students,
If I'm allowed to say a word then: "Thanks".

This is taken from a song: "Zion" by Lauren Hill
But then an angel came one day
Told me to kneel down and prey
For unto me a man child would be born
Woe this crazy circumstance
I knew his life deserved a chance
But everybody told me to be smart
Look at your career they said
"Lauren baby use your head"
But instead i chose to use my heart

Exactly. One day, I decided to take you, a group of children and not
and let you enter a new world. This has been my mission.

It is not about electronics, It is not about money, It is not about
and It is not even about resume.

What is "It" then?
There are very profound questions to which we don't know how to answer:
Where do we come from?
Why are we here? Or, why were we born?
Where are we going?

Compared to this questions, what is a common source amplifier becomes
ridiculous. It is not only if we put it in a broader context, the
of global knowledge.

Born again in a different world and
instruct you how to live in it; this should be all teachers' goal. I
believe that in the world of knowledge "Everybody's life deserve a
regardless of race, money, and even IQ.

The songs then go ahead and says:
"Now the joy of my world is in Zion" (Zion is her son).
Yes, today the joy of my world is in the wonderful class to which I say

Be free from stereotypes.




11 August 2004

I have posted lec. 14,16,19.
Lec. 14 and 16 are on mosfet, lec. 19 is on logic minimization.



10 August 2004

Answers to some questions tha tI have received:

I'm not quite sure what you mean by the output range being V_DSmax -
V_Dsmin. I found the output to equal -V_GD (although I can write the
output in terms of V_DS if I need to.) Then I found the output range to
V_GDmax - V_GDmin = V_DS. Am I doing this correctly? I also got V_DS as
the maximum input range.

A: The input rage is limited by the small signal approximation because
asking "what is the input range in order for the small signal analysis
hold". So you have to consider this. For the output range, you have to
keep the transistor in saturation!!!!

I have a small problem . I am taking this other class this summer, and
exam for that class is bering held during the class hours
that is from 10-11:30 am on thursday itself, and you have put the exam
from 11-1:30 i cannot make it, would it be possible for you to
shift the exam by 1 hour  instead of starting at 11 could you start at
pm, so that i can make it to the  exam, as my ECON exam is in Dwinelle
its quite a walk from Dwinelle to Cory.

A: The final is going to be on Th. from 12 to 2PM

It seems that to put Vgs > Vt, VI needs to be negative (and |Vi| <
Is this what you're intending? Or am I completely missing something?

A: I think this is correct. Anyway, I received a lot of questions of
type. Basically you know what you should do but you are afraid to make
mistakes. Then, it is true that this is the age of man (or the age of
reason) as opposed to the age of Heroes (or the age of immagination)
(thi is taken from Giovan Battista Vico).

For A.2 and C.1, the small signal expressions, we should assume that
is not 0, right? The C.1 gain expression is pretty complicated when
and r_d2  are nonzero.

A: Designing a PDA that can make phone calls, play DVDs, surf the
while having his battery last in 20days is complicated. The expressions
could be long but still lagebraic...

Using De-Morgan laws (x + y)' = x'y' ==> x + y = (x'y') in computing
S3 should be equal to (b'(a'c')'(ac)')' instead of b'(a'c')'(ac)',
S3  = (b'(a'c')')' + ac = (b'(a'c')'(ac)')'.
Thus, we don't need to have one more nand gate added to the output in
order to get S3, because S3 can be obtained by using 4 inverters and 3
nand gates  as shown in figure 2.

A: Right

In A, ( as you have corrected in class) your equation of I sat is I = k
(Vgs - Vt) ^2; did you mean there to be a factor of  in the equation? I
mean is it supposed to be I = k/2 (vgs-vt)^2?

A: Yes

In B2, did you mean for the capacitor to be discharged when t=0? If you
let the capacitor to be charged, then isn't the circuit going to start
sat mode and then stabilize in sat mode?

A: For t<0 the transistor is in cutoff. So the capacitor can charge at
because basically the transitor is an open circuit.

  Professor Pinto, can you fix the deadline for the hw at some time, so
that you can post the solution, and we can understand the problems
for the

A: If most people agree, the deadline could be fixed on Wednesday by

9 August 2004

My dear Students,
I have posted lab 13, as usual no pre-lab is required during exam week.

I have to apologize for not having all the lectures posted but I have
three deadlines in one month and I have to spend also some time for
research. I'll do my best.


6 August 2004

Dear Students,
This e-mail is long but please read it till the end because there are a
lot of important things.

I have posted solution to HW3. Please read it! Especially the last two
problems because most of you have done them by intuition without
following a method.

I have posted lecture 18, you may want to take a look at it before
tomorrow's class.

There are some people that didn't finish the lab where you were
to put everithing together. If you want to debug and finish your
experiment then you can go to lab whenever it is open even it is not

The final exam is going to be on 8/12 and not 8/13 because some
have problems in coming the 13th. I suggest to meet at 11AM, work on
the final until 1.30PM. Then I will go for lunch at Jupiter and if you
want we can go together.



03 August 2004

has been posted.

This hw might seem complicated but it's not.
Do the practice problems from the book first and then start with the


31 July 2004

Lab 11 and 12 have been posted on-line.
Please take a look at them.

Have a nice weekend

27 July 2004

Dear students,
I have posted solutions to HW2 and lecture 10 (which you don't really
about now).

I have to correct myself. In an excess of formality I gave you a
for computing the modulus of a ration of two complex numbers.
Even if the formula is correct, Renaldi was right and you can just
the ratio of the two abs.

so if z1 and z2 are complex number then

|z1/z2| = |z1|/|z2|

So now, citing one on my favorite scientists

"Do not worry about your problems with mathematics, I assure you mine
far greater" (I'm pretty sure that you knoe who the guy is).

Good night


27 July 2004

Since I really care about your stress level (you might want ot consider
that stress causes memory loss) and since some of you asked, HW3 due
is posteponed to Friday 5PM sharp.
This time I ask you to turn in the homework on time, late homework will
not be graded.


26 July 2004

Is now on-line.
If you have time, take a look at it before tomorrow morning.
There is no pre-lab to turn in.

As usual, we could have a review session tomorrow night.
Unfortunately the whole day if pretty busy.
I could do it from 8PM till 9PM.
I'll be there at 8PM if somebody shows up...


26 July 2004

Dear All,
Lab 9 is on-line. Since you have a midterm on Wednesday I'm not
you to do any pre-lab.
The report is required as usual.



20 July 2004

Dear All,
I received the following feedback:

I think it is VERY IMPORTANT that you do the basic stuff we need to
learn in EE40, provide more explanation and easy examples BEFORE you
talk you about extra stuffs (that are not in previous years)

Thank you very much for sending it!

There is an on line poll to understand whether it is a common feeling.
Please vote, it is very important for me to understand how should I
proceed with lectures. Also if you want to send me a more complete
answer, please feel free to drop me a line in the feedback form.



There are no problems for me in adjusting my style to your needs.
Actually, it would be much easier for me to reuse previous years slides
(or material in general) and to follow the book. Preparing the kind of
lectures that I'm giving is very time consuming for me because I have
simplify them as much as possible.
There are so many important details that I'm omitting from lectures
makes it very difficult to explain you things. Still, I think that you
have now a pretty broad knowledge that allows you to design complex
systems (but maybe you have not yet realized it). For instance, I think
you can easily sketch the block diagram of a television: form power
supply to the CRT driver circuit, to sound elaboration.
Sorry for being to tough with you.



18 July 2004

I received few questions concering HW2.
I'm answering to the mailing list because the questions could be
usefull for

1. Should we assume that the v in question A can be a sinusoidal
source (similar to what the textbook does on p. 157), or is it a DC
I'm asking this because if v is a sinusoidal voltage source, it can
the values of A and B in question A.3.II.

Yes, we assume that it is a sinusoid and we do a steady state
V will affect A and B only by its angular frequency. A and B will not
on time because the relation that you will find (which invole sin and
must be valid at any time so the time dependency will be lost (as I
shown in class).

Concerning homework problem C part 2. Knowing that the circuit actually
models a circuit with a capacitor with the initial voltage Vcc*R2/(R1 +
resistor R3, and a voltage generator initially set at -Vcc, I was
trying to
find the time when the capacitor will be discharged and recharged until
voltage across it is equal to the current Vy, -Vcc*R2/(R1 + R2), after
the source -Vcc will change polarity to Vcc. My circuit looks like

ground - capacitor - R3 - voltage source -Vcc - ground.

Using Kirchoff Voltage Law, I got Vcapacitor + Vcc = IR3. Also
utilizing the
equality I = C dv/dt, I changed the function into a differential
and attempted to solve for Vcapacitor with respect to time.
the answer came out to be Vcap = e^(t/R3). Since function of e would
be negative, the voltage across the capacitor, consequently Vx, will
-Vcc*R2/(R1 + R2). Not able to find the time in which Vx reaches Vy, I
cannot calculate the period of one cycle, and eventually the frequency,

I think the problem is the solution of the differential equation. The
solution should be something like
Vc=Vcc*R2/(R1+R2) e ^(-t/(R3*C)) - (1-e^(-t/(R3*C))*Vcc

This equation can give a Vc as low as -Vcc.


 I'm not sure how to analyze the circuit given in question C) of this
assignment.  Since the input voltages are not initially the same, I'm
assuming we need to do some sort of transient analysis, but I'm not
what model we should use for the op-amp.  Do we just use the standard
with the large input resistor and high-gain dependent source, defining
parameters as needed?  Or am I totally missing the correct method
altogether?  Also, I'm not sure why the output will oscillate if there
only one reactive element in the circuit, wouldn't this be a
circuit, implying that the output should decay exponentially?

Yes this is a good approach. Use a voltage controlled voltage source
and infinite gain and an input conductance equal to 0.
Remember that this circutis is not linear so you cannot apply the
of the second order circtuit. If you have a linear system that in order
oscillate it must be a second order circuit (or mode that second order,
there is a condition in order to have ascillation which is that the
order equation has two imaginary conjugate  roots).

In HW#2 A.4), I think you assumed that the gain of 2nd order circuit is
So you gave us the problem A.4) " I) Solve the equation : sqrt(A^2+B^2)
1/sqrt(2) "
But I think the gain of this 2nd order circuit is not 1.
(It depends on values of R1, R2, C1, C2).
And even though the gain is 1, the equation, sqrt(A^2+B^2) = 1/sqrt(2),
too complex to solve by hand.

The gain depends on the frequency of your circuit. There are two
for which the gain is 1/sqrt(2). You have to find them.

Hope this helps.

Ps.: only two students asked a review for the lab so I think I'm not
to do it also because I have to leave at 5.45PM.



16 July 2004

My Dear Students,
Lab7 is on-line.
The pre-lab is a little bit long and I know that this lab is not easy.

Look at it without fears, you are the master and the circuit is your
don't ever feel that it is the other way around (is like with dogs, if
are afraid of them they will byte you).

If you have problems understanding the circuit, it is no your fault by
your instructor fault.
So if there are many requests I could spend 1 hour on Sunday (from 5PM
6PM) with you to explain the circuit.

Have fun!


14 July 2004

Dear All,
I have added:
-a link to software for mac os
-Other classes around US under links->education
-References to books you might want to borrow/buy under

Please, don't borrow the books from the library forever. Borrow them,
the part that you need in 30 minutes (maybe *copy* the pages in your
and return it.

Have fun


13 July 2004
Dear All,
Sorry for the late notice.
Lab 6 is on line. Since it is late, the prelab is very easy.

The report though, has two questions that you are supposed to answer
The first is a yes or no question, the second will require you to
reason a
little bit.

Have fun


PS.: you would probably like to look at the notes from today's class.
going to post them in 10 minutes.

13 July 2004
Somebody asked me the spice netlist but I don't remember who.
I'm sending what comes out form 5spice.

Hope this helps.


12 July 2004
Dear All,
HW2 is on-line.

I know that this class is very intensive, I also know that I'm pushing
too much (maybe) while you are more interested in seeing practical
but please spend a little time in trying to understand the homework.
do the homework just because it is a duty, try to give your own
interpretation to the problem and to understand the hypothesis and
implication (i.e. the results).

Tomorrow, I don't  know if I can start with semiconductors. I think we
to do the following first:

1)Fix few things: thevenin and norton  equivalence and a general method
analyze circuits with op-amps
2)Find a way of analyzing RLC circuits.

Remember one thing. We know how to solve circuits (node-voltage and
mesh-current). We always try to reduce whatever new problem to standard
analysis methods.
Things you'll see tomorrow are all aimed to that.

Goodnight (even if night is almost over)


10 July 2004
Lab 5
Is on line.
There is a prelab this time.



9 July 2004

Dear All,
I posted solutions to most of the review problems (which I posted this
I hope this can help.

But "There is a flip side to that coin" (Robert de Niro, Heat, 1995), I
could not prepare the lab. I'm going to do it now.


8 July 2004

Dear All,
Remember the class tomorrow (Th) from 5 to 7PM in 277 Cory Hall. After
I can review few things and solve problems if you want.

The second step you have to do is to build a tone controller. In order
to do
that you need to be able to measure bandwidth an other things.
Friday will be dedicated to the use of scope and function generator.
Friday is also midterm day, I will not require any pre-lab but please
for the midterm.

Even if the homework is ready I will not post it until tomorrow because
don't want to look at it before the midterm. Please, FOCUS on the
I will post few problems tomorrow morning before 9AM. Please work on
them so
that we can go over them in the review session.



3 July 2004
Dear All,
Lab3 is on line. Go to labs->lab3.
There are few questions that you have to answer and turn in at the
of the lab.

28 June 2004
Dear All,
Tomorrow's lab is going to be on Spice, a program for circuit simulation.
Please, take a look to the manual (which is posted under "Labs" on the
class website). If you want to can intall one of the millions of versions of
spice (I have put a link on the labs page).
Besides the elegant thory that I have shown you in class, I have to say
that spice uses the MNA (modified voltage analysis) to solve circuits which
is the node-voltage analysis where you add as many extra equations as
voltage sources (in order to avoid a postprocessing phase to retrive the
original topology).
Homework 1 is posted on-line. Use the method that you prefer: MNA,
transformation, supernode, supermesh etc. but you have to use both
node-voltage and mesh-current. If you really want to undestand I
suggest you
to try evething that bounce in you mind and verify that the result is
the same.
There is a link on the website for anonymous feedback. It is very
to me, just click on the link and drop me a line.